JPH0635410A - Projection type display device - Google Patents

Abstract

PURPOSE:To reduce deterioration in light emission due to an increase in the current density of the fluorescent body of a B projection tube without any deterioration in resolution. CONSTITUTION:The B projection tube 4B is specially provided with a modulation coil 11 and a current for horizontal modulation (at frequency higher than horizontal scanning frequency) is supplied from a scan modulating circuit 10 to make a horizontal scan while moving up and down the electron beam for the horizontal scanning zigzag. The scanning speed on the fluorescent body increases and the electron beam increases in equivalent current density, so the deterioration in the light emission efficiency of the fluorescent body is reducible. The device is used in no out-of-focus state, so the resolution deterioration is small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device for displaying a color image by synthesizing lights from respective red, green and blue projection tubes on a screen, and more particularly to a bright display image and a high resolution. It relates to a good such projection display device.

[0002]

2. Description of the Related Art Projection type display devices include red, green, blue (hereinafter,
Images projected from three projection tubes corresponding to R, G, and B (abbreviated as R, G, B) through a projection lens are combined on a screen to form and display a color image.

Here, the brightness of the display image on the projection tube is much higher than the brightness of the direct-view type display image for directly looking at the CRT because the display image corresponds to a reduced image of a normal image on the screen. It's getting higher. Therefore, the electron beam per unit area input to the phosphor of the projection tube
The energy is very large, and a phosphor with good characteristics is used under such conditions.

However, the B (blue) phosphor does not have a good luminous efficiency at high current density, and is generally inferior to R and G in efficiency. Further, the efficiency becomes worse as the screen becomes brighter, that is, in the high current region, and the gamma characteristic representing the inclination of the luminance with respect to the drive voltage of the projection tube becomes smaller as the luminance becomes higher.

On the other hand, the maximum driving voltage of the projection tube is
Since R, G, and B are the same, in order to set the color temperature when displaying white to a desired value, the brightness of white is limited by the brightness of B, which has low efficiency. Therefore, it is necessary to improve the efficiency of B in order to increase the brightness of the display image. Furthermore, since the gamma characteristic is different for B, R, and G, the color temperature changes depending on the brightness of the displayed image.

In order to solve such a problem, in the conventional projection display device, only the projection tube of B is defocused, the size of the electron beam spot is increased to reduce the current density to the phosphor, and The luminous efficiency is improved.

As a related document describing this type of technique, for example, Japanese Patent Application Laid-Open No. 3-123287 can be cited.

[0008]

In the above prior art, B
Since the focus of the B projection tube is blurred in order to improve the luminous efficiency of B, the resolution of the image deteriorates. In particular,
In a specific pattern such as white letters, B protrudes from the contour, making the screen difficult to see.

It is an object of the present invention to provide a projection type display device capable of overcoming the drawbacks of the prior art and improving the luminous efficiency of B without blurring the focus of B.

[0010]

In order to achieve the above object, in the present invention, instead of blurring the focus of B, B
By making the scanning speed of the electron beam of (1) with respect to the fluorescent surface higher than that of R and G, the density (current density) of the electron beam hitting the phosphor is reduced and the luminous efficiency of B is improved.

[0011]

In stead of blurring the focus of B, the scanning speed of the electron beam with respect to the fluorescent surface is increased to improve the luminous efficiency of B, so that the deterioration of resolution can be reduced.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a projection display device as an embodiment of the present invention.

In the figure, 1R, 1G and 1B are R, G and B video signal input terminals, 2 is a sync signal input terminal, 3 is a video circuit, 4R, 4G and 4B are R and G respectively.
G, B projection tubes, 5R, 5G, 5B are R, G,
B deflection yoke (hereinafter abbreviated as DY), 6R, 6
G and 6B are R, G, and B convergence yokes (hereinafter abbreviated as CY), 7 is a deflection circuit, 8 is a high voltage circuit, 9 is a convergence circuit, and 10 is a scanning modulation circuit.
Reference numeral 1 is a modulation coil.

Reference numerals 12R, 12G, and 12B are schematic views showing scanning states of electron beams on the R, G, and B projection tube surfaces, respectively. Of the above configurations, the scanning modulation circuit 1
The configuration except for 0 and the modulation coil 11 is the same as the configuration of the conventional general projection display device, and thus detailed description thereof will be omitted.

In this embodiment, when the same high drive voltage as that applied to the R and G projection tubes is applied, the brightness characteristic is saturated, and the modulation coil 11 is specially provided only to the B projection tube 4B. Further, the scanning modulation circuit 10 drives the modulation coil 11 at a frequency higher than the horizontal scanning frequency so that the electron beam scanning in the horizontal direction scans vertically while moving vertically.

The modulation coil 11 may be driven in synchronization with the deflection circuit 7 as shown in FIG. 1, or may be driven by the scanning modulation circuit 10 alone. The amount of vertical movement of the electron beam during horizontal scanning (the amount of vertical movement that repeats vertical movement) is about the scanning line interval of horizontal scanning lines, which is shorter than the horizontal scanning period. ,
The normal scanning line on the tube surface is linear as shown by 12R and 12G, whereas in 12B, the scanning line shape is zigzag modulated in the vertical direction.

For this reason, the electron beam of the B projection tube 4B relatively increases the speed at which the electron beam scans the tube surface, and the current density for the phosphor decreases. Therefore, the luminous efficiency of B can be improved, and the saturation of the brightness characteristics can also be reduced.

Next, FIG. 2 shows that the present invention is superior to the conventional method of defocusing to increase the spot diameter of the electron beam and reducing the current density.
Will be described below. FIG. 2 is an explanatory diagram of the operation principle showing the operation principle of the present invention in comparison with the conventional method for blurring the focus.

FIG. 1A shows the current distribution of the electron beam and the scanning locus at the time of just focusing without any measures. That is, the current distribution of the electron beam is such that the current density is maximum at the center of the electron beam spot and the current density decreases as the distance from the center increases in the radial direction. The electron beam spot follows a scanning locus in which it travels linearly in the horizontal direction.

FIG. 2B shows the current distribution and scanning locus of the electron beam according to the present invention. That is, the current distribution of the electron beam is the same as that of (1) in FIG. 2, but this electron beam spot follows a scanning locus in which it travels in the horizontal direction while zigzag in the vertical (vertical) direction. is there.

FIG. 2C shows the electron beam current distribution and scanning locus due to conventional focus blurring. From the blurring, it can be seen that the diameter of the electron beam spot becomes large and that it travels linearly in the horizontal direction.

2 (1), (2), and (3) show loci of the same time interval, and the locus of the invention (2) is
Since the distance traveled during the same time is longer than that of the trajectory before the countermeasure (1), and therefore the speed of the electron beam with respect to the phosphor is faster, the current density is relatively reduced, and the luminous efficiency of the phosphor is reduced. Deterioration is reduced.

On the other hand, in the conventional method for blurring the focus (3), the entire current density is reduced as compared with that before the countermeasure (1) because the tail of the current density distribution is widened. However, since the electron beam passes along a straight line, the current density is still large, and the difference in current density from the surroundings is large.

Therefore, the relative current density of the phosphor passing through the center of the electron beam in consideration of the speed of the electron beam has not decreased so much, and the area of the electron beam has expanded, but the effect of the central portion has been increased. Is few. In the present invention, since the central portion with a large current density scans a wide range on the phosphor screen as shown in the figure, the maximum value of the relative current density becomes small, resulting in a more averaged current density. , The brightness improving effect is improved.

On the other hand, in the present invention, since the focus of the electron beam is not blurred, the resolution in the horizontal direction is the same as that at the time of just focus before the countermeasure, and the resolution does not deteriorate unlike the method of blurring the focus. In addition, as for the vertical resolution, the brightness improving effect is also improved. Therefore, if the same brightness improving effect is to be obtained, the equivalent vertical spot diameter of the electron beam can be reduced. It is possible to reduce the deterioration of the vertical resolution of the method as compared with the method of blurring the focus.

Next, a second embodiment of the present invention will be described below with reference to FIG. FIG. 3 is a block diagram showing a schematic configuration of a projection type display device as a second embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The embodiment shown in FIG. 3 is different from that shown in FIG. 1 in that instead of the scanning modulation circuit 10 and the modulation coil 11 provided in FIG. 1, a convergence circuit 20 and a B circuit are provided.
CY6B for scanning is also used for scanning modulation, and the modulation waveform generating circuit 2
9 is newly provided.

The convergence circuit 20 includes a convergence correction waveform generation circuit 21 and output amplifiers 22, 23 and 2.
4, 25, 26, 27, and each of R, G, B is composed of 6 circuits in the horizontal and vertical directions.

In the present embodiment, this convergence circuit 2
Of the 0 output amplifiers, the scan modulation waveform from the modulation waveform generation circuit 29 is superimposed on the input of the B vertical output amplifier 27 by using the adder 28. This allows C for B
Since the scan modulation can be performed by Y6B and the scan modulation similar to the case of FIG. 1 can be performed, the same effect as that of FIG. 1 can be obtained.

Furthermore, regarding the third embodiment of the present invention,
This will be described below with reference to FIG. FIG. 4 is a block diagram showing a schematic configuration of a projection type display device as a third embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The embodiment shown in FIG. 4 is different from that shown in FIG. 1 in that instead of the scanning modulation circuit 10 and the modulation coil 11 provided in FIG. 1, a modulation waveform generating circuit 37 and a vertical deflection for B are provided. The circuit 36 is newly provided, and the vertical coil of DY5B for B is also used as the modulation coil.

Accordingly, the main deflection circuit 35 shown in FIG. 4 is a circuit obtained by removing the vertical deflection portion for B from the deflection circuit 7 shown in FIG. The B vertical deflection circuit 36 also performs scanning modulation in accordance with the modulation waveform from the modulation waveform generation circuit 37 in addition to the normal vertical main deflection. As a result, the same scanning modulation as that of FIG. 1 can be performed, and the same effect as that of FIG. 1 can be obtained.

A fourth embodiment of the present invention will be described below with reference to FIG. FIG. 5 is a block diagram showing a schematic configuration of a projection type display device as a fourth embodiment of the present invention. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

The embodiment shown in FIG. 5 is different from the embodiment shown in FIG. 1 in that a modulation amplitude control circuit 39 for controlling the output amplitude of the scanning modulation circuit 10 is newly provided. The modulation amplitude control circuit 39 controls the output amplitude of the scanning modulation circuit 10 to B
Is changed according to the size of the input video signal.

This is because when the input signal of B is small and the beam current is small, the luminance deterioration of the phosphor is small, and when the input signal is large, the beam current increases and the luminance deterioration becomes large. In addition, control is performed so that the amplitude of scan modulation is optimized. Although the modulation amplitude control circuit 39 is used to control the input video signal of B in FIG. 5, it may be used for control by directly detecting the cathode current of the B projection tube 4B.

With the above structure, the value of the modulation amplitude becomes small at a low beam current which causes little luminance deterioration and does not require scanning modulation, so that the effect of reducing resolution deterioration is further improved as compared with the embodiment of FIG. In addition, in FIG. 5, although it is applied to the first embodiment, the same effect can be obtained by applying it to the second and third embodiments.

Next, a fifth embodiment of the present invention will be described below with reference to FIG. FIG. 6 shows the fifth aspect of the present invention.
2 is a block diagram showing a schematic configuration of a projection display apparatus as an embodiment of the present invention. The same parts as those in FIG.

In FIG. 6, unlike the above-described embodiments, instead of scanning and modulating the electron beam of B, only B is horizontally scanned like the tube surface 50B of FIG. 6 showing the scanning of the B projection tube 4B. The speed is doubled.

This corresponds to the deflection circuit 7 and the convergence circuit 9 shown in FIG.
A deflection circuit 40 for G, a convergence circuit 41 for R, and G are provided. For B, a double speed deflection circuit 42 for B having a horizontal scanning frequency of 2 and a convergence circuit 43 for B synchronized with the double speed deflection circuit 42 for B are newly added. It is realized by installing it in.

However, since the input video signal of B and the double speed deflection circuit for B 42 cannot be synchronized in this state, R and G corresponding to the video circuit 3 of FIG. 1 excluding the portion for B.
It is divided into a video signal circuit 44 for B and a double speed conversion video circuit 45 for B, and the input video signal for B only is converted at a double speed to synchronize with the double speed deflection circuit 42 for B.

As a result, the equivalent current density of the electron beam is reduced to half, and the deterioration of brightness can be greatly reduced. Further, since B is not just vertically focused and vertically modulated, there is no deterioration in resolution.

[0042]

As described above, according to the present invention,
In the projection display device, the luminous efficiency of the B projection tube can be significantly improved, and the deterioration of resolution can be suppressed to the minimum. As a result, the display image quality of the projection display device can be significantly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a projection display device as a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation principle showing the operation principle of the present invention in comparison with a conventional focus blurring method.

FIG. 3 is a block diagram showing a schematic configuration of a projection display device as a second embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a projection display device as a third embodiment of the present invention.

FIG. 5 is a block diagram showing a schematic configuration of a projection display apparatus as a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a schematic configuration of a projection display device as a fifth embodiment of the present invention.

[Explanation of symbols]

3 ... Video circuit, 4 ... Projection tube, 5 ... DY, 6 ... CY, 7
... Deflection circuit, 8 ... High voltage circuit, 9 ... Convergence circuit,
10 ... Scan modulation circuit, 11 ... Modulation coil, 12, 50B
... Schematic diagram showing scanning of electron beam, 21 ... Convergence correction waveform generation circuit, 22-27 ... Output amplifier, 28 ...
Adder, 29, 37 ... Modulation waveform generating circuit, 35 ... Main deflection circuit, 36 ... B vertical deflection circuit, 39 ... Modulation amplitude control circuit, 40 ... R, G deflection circuit, 41 ... R, G convergence Circuit, 42 ... B double speed deflection circuit, 43 ... B convergence circuit.

Claims (6)

[Claims] 1. A scanning speed of an electron beam in a blue projection tube with respect to a screen phosphor in a projection display device for displaying a color image by combining lights from respective red, green and blue projection tubes on a screen. Is made faster than that in the red or green projection tube, so that the density of the electron beam striking the blue phosphor is relatively reduced compared to that hitting the red or green phosphor. Projection display device. 2. The projection type display device according to claim 1, wherein the means for increasing the scanning speed of the electron beam in the blue projection tube with respect to the screen phosphor is faster than that in the red or green projection tube. A blue projection tube is provided with a modulation coil as a modulation means for vertically modulating the horizontal scanning of the electron beam in addition to the horizontal and vertical scanning associated with the normal operation of the electron beam. Projection display device. 3. The projection display device according to claim 1, wherein the scanning speed of the electron beam in the blue projection tube with respect to the tube surface phosphor is higher than that in the red or green projection tube. A projection display device, comprising: a convergence yoke that corrects a blue electron beam in a vertical direction, and means for superimposing a correction waveform current that modulates a horizontal scanning of the electron beam in a vertical direction. 4. The projection type display device according to claim 1, wherein the means for increasing the scanning speed of the electron beam in the blue projection tube with respect to the screen phosphor is faster than that in the red or green projection tube. A projection type display device characterized in that means for superposing a modulation waveform current for vertically modulating a horizontal scanning of a blue electron beam is provided on a vertical coil of a deflection yoke of a blue projection tube. 5. The projection display device according to claim 1, wherein the scanning speed of the electron beam in the blue projection tube with respect to the screen phosphor is faster than that in the red or green projection tube. A projection type display device comprising means for increasing the horizontal scanning frequency of an electron beam deflection circuit in a blue projection tube to twice that in a red or green projection tube. 6. The projection type display device according to claim 2, 3, 4 or 5, wherein the scanning speed of the electron beam in the blue projection tube with respect to the tube phosphor is faster than that in the red or green projection tube. A projection type display device, characterized in that means for controlling the above-mentioned means according to the magnitude of a blue input video signal is provided.